This invention relates to a method and an apparatus for treatment of gas mixtures, such as biogas or flare gas, and in particular to a method and an apparatus for removing contaminants, in particular hydrogen sulphide, from a gas mixture comprising hydrogen sulphide, in particular hydrogen sulphide and methane.
Gas mixtures produced and used in industry may contain contaminants.
For instance, biogas is a gas mixture that can be produced by anaerobic digestion with anaerobic bacteria, which break down the organic carbon in the raw materials to a biogas which is mainly comprised of methane (CH4) but which contains contaminants such as carbon dioxide (CO2) nitrogen (N2) and hydrogen sulphide (H2S).
When natural gas is produced as a by-product of industrial processes, for instance in oil industry, operators will often vent or flare the gas mixture produced. This gas is commonly called flare gas. It is common that flare gases are contaminated with H2S. Flare gases commonly also contain methane.
H2S is very harmful to the environment and human health. It generates an unpleasant smell and even at very low concentrations it can be life threatening. Moreover, it is detrimental to combustion engines. Apart from that, H2S is in the combustion process converted to sulphur oxides (SOx), which are also harmful to the environment and human health.
Methane can be combusted or oxidized with oxygen to release energy. This energy release allows biogas to be used as a fuel. It can for example be used in gas engines.
There is a continuous need in industry for improved methods and apparatuses which purify methane to acceptable levels of purity and which remove H2S from gas mixtures.